Clutch



K. MILLER June- 23, 1942.

CLUTCH Filed Nov. 24, 1941 Illlllllltorily with fairly coarse a Patented June 23, 1942 Kay Miller, Rockford, Vacuum Machine 111., assignor to The Atwood Company, Rockford, 111., a

partnership composed of Seth B. Atwood and James T. Atwood Original application April 12, 1941, Serial No.

388,283. Divided and this application November 24, 1941, Serial No. 420,198

2 Claims. (Cl. 192-68) This application is a division of my copending application Serial No. 388,283, filed April 12, 1941.

This invention relates to friction clutches and is more particularly concerned with over-center type clutches especially designed for tractors, although suitable, of course, for other heavy duty purposes.

The principal object of my invention is to provide an over-center type clutch of simple, economical, and practical design and construction obtaining substantially constant engaging pressure regardless of wear and operating satisfacd infrequent adjustment. l, Y

The invention is illustrated in the accompanying drawing, in which- Fig. 1 is a longitudinal section through a clutch made in accordance with my invention, the same being shownin disengaged position, and

Fig. 2 is a fragmentary sectional detail illustrating a variation in the construction of Fig. 1.

The same reference numerals are applied to corresponding parts in these two views.

Referring first to Fig. l, the end portion of the crank-shaft of the engine is indicated in dotted lines at it) and the flywheel at H. i2 is the driven shaft extending rearwardly, from the flywheel and clutch into the gear box of the transmission in the usual way. This shaft has the usual pilot bearing at i 3 supporting the front end thereof at the center of the flywheel. I4 is the clutch disk, the center hub iii of which is splined on the front end of the shaft l2 to transmit drive from the flywheel to the shaft when the clutch is engaged. The usual pads or facings IE on the clutch disk are engageable with the driving face I! on the flywheel and the compansion driving face i8 on the pressure plate Ill. The latter is suitably cast like the flywheel, the faces I! and. is being accurately machined to insure smooth clutch engagement. The back plate is also a'casting and is arranged to be bolted at 20' to the rim of the fiywheeL: Small rectangular plates 2|, fitting in radial grooves 22 in the rim of the back plate, are secured in place by rivets 23 and have a working fit in radial grooves 24 in the rim portion of the pressure plate ill to' drive the pressure plate with the flywheel, while allowing axial movement of the pressure plate relative to the flywheel, as required in the engagement and disengagement of the clutch. Bolts 25 are entered freely through holes 26 in the plates 2i and threaded in holes 21 in the pressure plate to provide mountings for coiled compression springs 28 acting between the plates 2| and the heads of the bolts 25, as shown, to urge the pressure plate normally away from the flywheel and clutch disk to retracted disengaged position.

The pressure plate I! carries a sheet metal ring 29 on the back thereof on screws 30, the ring being of generally channel-shaped crosssection'and disposed in concentric relation to the pressure plate. Spacer collars 3| form guides for the ring 29 and are clamped by the screws against the back of the pressure plate, the collars fitting freely in holes 32 in the web portion 33 of the ring and having annular flanges 34 engaging the web portion alongside the holes 32. Lock washers 35 between the heads of the screws 30 and the collars 3| prevent loosening of the screws once they are tightened properly. The screws 30' are provided in circumferentially spaced relation on the pressure plate. Coiled compression springs 36 are also provided in circumferentially spaced relation with respect to the pressure plate l9 between seats 31 on the back of the pressure plate and stamped sheetmetal cups 38 entered in holes 39 provided therefore in the web portion of the ring 29. These springs are preloaded to an extent determined by the collars 3i, which, it will be easily understood,

limit the extent to which the springs 36 can be compressed by the tightening of the screws 30. The term preloaded signifies thatupongenga'gement of the clutch the springs 36'are subjected to further compression, and it is this'increased spring pressure that is effective on the pressure plate to hold the clutch disk It engaged between the flywheel and pressure plate. The further compression of the springs is obtained by movement of the ring 29 relative to the collars 3| toward the pressure plate i9, such movement being given the ring in the engagement of the clutch by the actuating levers 40. A plurality of these levers are provided in equally circumferentially spaced relation with respect to the back plate 20, being pivoted, as at 4|, on cars 42 provided on a sheet metal ring 43 rotatably mounted on an annular flange 44 provided on the inner side of the back plate in concentric relation with the flywheel and pressure plate. vIn that way the ring 43 is supported in concentric relation to the ring 29, so as to maintain proper relationship between the finger projections 45 on the intermediate pivot portions of the levers 40 and cam means 46 extending circumferentially with respect to the inner flange ll of the ring 29. That is important because the ring 43 is arranged to be ad- Jllsi ed rotatively relative to the back plate to adjust the flnger portions 45 of the levers relative to the inclined helical cam surfaces 45 on the correlated arcuate segments 45 of the circumferentially extending cam means 45 to compensate for wear on the clutch disk facings l5. The segments 45, of which there happen to be six, one for each of the six levers 40, are formed from straight strips of sheet metal formed to the desired arcuate shape and entered with a press flt in a sheet metal ring 50 of channel-shaped cross-section, which, in turn, is pressed into place on the inner flange 41 of the ring 29. The ring 43 has an inner annular flange for reinforcemerit and an outer annular flange 52 which also lends strength and rigidity to the ring. However, the edge of the flange 52 is notched circumferentially, as indicated at 53, to permit using a screw driver or other tool to turn the ring 43 in the adjustment of the clutch. Inspection holes 54 in the back plate leave the notched edge of the ring exposed for such adjustment. A gear 55 meshing with the notched edge 53 of the ring 43 is mounted inside the back plate 20 on a screw 55, which is threaded in the center of the gear but has a free flt in the hole 51 in the back plate so that the gear can be used to lock the ring 43 in adjusted position by merely tightening the screw and thus clamping the gear tightly against the inner face of the back plate. A cross-pin 55 on the inner end of the screw 55 limits the unthreading of the screw 55, so that the workman cannot disconnect the screen from the gear. Obviously when the screw 55 is loosened, the gear 55 will turn freely along with the screw when the ring 43 is adjusted, and thereafter the tightening of the screw 55 clamps the gear 55 and thus holds the ring 43 securely in adjusted position.

The levers 40 project through slots 59 in the ring 43 for pivotal connection, as at 50, with toggle links 5|, which, in turn, are pivotally connected at 52 with lugs '53 on a throw-out collar 54. The flat surface 55 on the front of each lug 53 serves by engagement with the edge of the inner flange 5| on the ring 43 to limit the forward movement of the throw-out collar in the engagement of the clutch when the pivots 52 have moved past a plane through the pivots 50 normal to the shaft I2; in other words, when the toggle links 5| for operating the levers 40 have been moved over center." Each of the levers 40 has an arm 55 extending forwardly from the pivot portion of the lever and enlarged at the outer end, as indicated at 51, to serve as a counterweight, the centrifugal force on which-will balance the centrifugal force on the rear end portion of the lever and thus eliminate that as a factor in the operation of the clutch. The throw-out collar 54 is operable back and forth by means of a ring 55 provided with trunnions 59 for cooperation with the usual yoke or other clutch operating means. This collar is provided with a lubricant fitting 10, whereby to insure adequate lubrication of the anti-friction bearing 1| between the ring 58 and the throwout collar 54. A sheet metal ring I2 fastened. asindicated at 13, to the back of the ring 58 serves both as a shield for protection of the brake facing ring 14 on the collar 15 and as a brake disk, the ring I! having the inner annular edge portion 15 projecting radially inwardly into close proximity with the periphery of the shaft II, as shown, to eliminate any likelihood of lubricant from the bearing ll finding its way onto the collar I5 and fouling the brake facing ring 14. The collar 15 is secured, as indicated at II, on the shaft I! to turn with the shaft and be held against endwise movement with respect thereto, so that when the clutch is disengaged and the throw-out collar 54 assumes the position shown in Fig. 1, the ring I2 is automatically brought into contact with the brake facing ring 14' to stop the spinning of the clutch disk l4.

In operation, the springs 35 are preloaded to approximately 165 lbs. and in the engagement of the clutch are compressed to exert at least 210 lbs. pressure on the clutch disk |4 through the pressure plate l5. It requires approximately .080" travel to change the compression from the preload pressure of 165 lbs. to the engagement pressure of 210 lbs. and it follows, therefore, that a few thousandths of an inch wear on the clutch disk facings l5 will not be noticeable and cannot seriously affect the operation of the clutch. By the same token it follows that the clutch will operate satisfactorily with fairly coarse and infrequent adjustment despite the fact that the present clutch is of the over-center type and over-center clutches have heretofore necessitated frequent accurate adjustments, because even a small amount of wear on the clutch disk facings caused an appreciable reduction in the engaging pressure and resulted in excessive slippage and accelerated wear on the faclngs.

In the construction disclosed in Fig. 2, each spring 35 has a stacked spring washer assembly 15 substituted therefor, each assembly consisting of two Belleville type spring washers l9 and with a spacer ring 5| therebetween, held in centered relationship with the washers within the curled or flanged peripheries 52 thereof. Each of these spring washer assemblies provides an initial or preload spring pressure of lbs., and in the engagement of the clutch the washers are compressed further to exert at least 260 lbs. pressure. These assemblies require only .030" compression to reach the preload pressure of 130 lbs., as compared with a .060" compression in the operating range to increase the spring pressure another 130 lbs. Hence the spring means 15 may, therefore, be described as having a low rate within its operating range. Thus there is little loss in engaging pressure for a given amount of wear on the clutch disk facings when springs of this type are employed. In passing, it will be understood, of course, that the clutch, only a portion of which appears in Fig. 2, is otherwise of the same construction as that disclosed in Fig, 1, and will operate otherwise in the same way asthe clutch of Fig. 1.

It is believed the foregoing description conveys a good understanding of the objects and advantages of my invention. The appended claims have been drawn to cover all legitimate modifications and adaptations.

I claim:

1. In a friction clutch, the combination with a flywheel constituting the driving element, and a clutch disk constituting the driven element, of a back plate for the flywheel, a pressure plate turning with the back plate and movable toward and away from the same in the disengagement and engagement of the clutch, respectively, a ring mounted for rotary adjustment relative to the back plate, circumferentially extending cam means on the pressure plate in concentric relation with said ring, one or more elongated levers extending in the general direction of the axis of rotation of said clutch but radially spaced therefrom, each pivoted intermediate its ends on said ring and having a radially projecting finger on the pivoted portion engaging the circumferentially extending cam means, a counterweight on one end of each of said levers, means including toggle links pivotally connected with the other end of said levers for oscillating the same to force the pressure plate away from the back plate to engage the clutch, said levers being adjustable with the ring circumferentially with respect to the cam means, and spring means held between the cam means and the pressure plate in preloaded condition and arranged to be compressed further by the action of said levers in the engagement of the clutch whereby to exert increased pressure on the pressure plate while the clutch is engaged.

2. In a friction clutch, the combination with a flywheel constituting the driving element, and a clutch disk constituting the driven element, of a back plate for the flywheel, a pressure plate turning with the back plate and movable toward and away from the same in the disengagement and engagement of the clutch, re-

spectively, a ring mounted for rotary adjustment relative to the back plate, circumterentially extending cam means on the pressure plate in concentric relation with said ring, one or more elongated levers extending in the general direction of the axis oi. rotation of said clutch but radially spaced therefrom, each pivoted intermediate its ends on said ring and having a radially projecting finger on the pivoted portion engaging the circumferentially extending cam means, a counterweight on one end of each of said levers, means including toggle links pivotally connected with the other end of said levers for oscillating the same to force the pressure plate away from the back plate to engage the clutch, a throw-out collar pivotally connected with the ends of said links remote from the levers and movable toward and away from engagement with the ring, said ring limiting move ment of the throw-out collar when the toggle links have been moved over center in the engagement of the clutch, said levers being adjustable with the ring circumferentially with respect to the cam means, and spring means held between the cam means and the pressure plate in preloaded condition and arranged to be compressed further by the action of said levers in the engagement of the clutch whereby to exer increased pressure on the pressure plate while the clutch is engaged.

' KAY MILLER. 

